“Greece will default,” Roach said in an interview on CNBC today. While the risk of such an event is “pretty close” to being priced in by investors, he said the potential knock-on effects are “definitely not baked in.”

Institutions would be able to handle a Greek default, regardless of the level of bondholder losses and the bigger concern is how it would affect Spain, Portugal, Ireland or Italy, Markus Beumer, a member of the German lender's board of managing directors, said.

Passos Coelho said it was crucial to ensure Portugal met the budget deficit targets required for the bailout. The government is doing this through sweeping spending cuts and tax rises which have pushed Portugal into a deep recession.